(1) Field of the Invention
This invention relates to an apparatus that uniformly scribes a coated panel for adhesion testing purposes.
(2) Description of Related Art
A wide variety of substrates are coated with single and often multiple layers of clear and/or pigmented coating compositions. The adhesion of the coating composition to the substrate is of concern and adhesion measurements by various methods have been developed and are in current commercial use. In one particularly useful adhesion test, an area of the coating on a panel is scribed through to the substrate and tape is applied over the scribed area. The tape is removed and the amount of the coating that has been removed is determined and the adhesion of the coating to the substrate can be rated. This makes it possible to compare the adhesion of various coatings. ASTM D3359 describes this adhesion test that is conventionally used.
The problem with this test and related tests is the scribing of the coating through to the substrate. There are a variety of hand held cutting devices available to scribe a coating, in particular, to scribe a pattern in the coating, for example, a crosshatch pattern on the coated substrate which usually is a test panel. With such hand held devices, operator variability, operator error and/or dull cutting edges on the device result in non-uniform and non-replicable scribing of the coating. For example, the scribed pattern applied by different operators depends on the pressure applied by the operator thereby varying the depth of the scribe. Also, on how steady the scribing tool is held by an operator can affect the width of the scribe and the sharpness or dullness of the cutting tool also will affect the scribe. Operator fatigue and long term muscular damage that can be caused by repeated scribing by an operator day after day has also been a problem.
There is a need for an apparatus that can rapidly scribe substrates in comparison to hand scribing, can easily be operated by a person with minimal effort without causing fatigue or physical injury to a person and the apparatus has to be safe, for example, from pinch points, must be ergonomically acceptable and must produce uniform and repeatable scribes or scribe patterns on a coated substrate. Every scribe or scribe pattern formed must penetrate the coating through to the substrate and must be uniform and repeatable. The novel apparatus of this invention accomplishes the above.